1. Field of the Invention
The present invention relates to a drive system for a motor vehicle including an electric machine for rotating a driveshaft of a drive unit and/or obtaining electrical energy from the driveshaft when the driveshaft is rotating, the electric machine having a stator arrangement and a rotor arrangement which is connected or connectable to the driveshaft for common rotation about an axis of rotation.
2. Description of the Related Art
German reference DE 198 31 384 C1 discloses a drive system with an electric machine arranged in the drive train of a drive unit for driving a drive shaft and for obtaining electrical energy from the drive shaft during rotation of the drive shaft. In this reference, the electric motor includes a rotor permanently connected to the crankshaft of the drive unit via a support. If wobbling movements induced by individual piston strokes of a drive unit occur in the region of the crankshaft which projects from the drive unit, these wobbling movements are transmitted to the rotor of the electric motor by the support. The rotor will execute a corresponding wobbling movement which changes the air gap provided between the rotor and the stator. The changes in the air gap alter the operating characteristics of the electric motor, particularly in the generator mode. Accordingly, wobbling movements of the drive shaft produce nonuniform operating characteristics.
It is the object of the invention to provide a drive system for a motor vehicle in which fluctuations in the operating characteristics of an electric machine induced by nonuniformities of movement are avoided.
This object is achieved according to the present invention by a drive system for a motor vehicle comprising an electric machine arranged for driving a drive shaft and/or obtaining electric energy from the drive shaft when the drive shaft is rotating. The electric machine has a stator arrangement and a rotor arrangement connected or connectable to the driveshaft for common rotation about an axis of rotation.
The rotor arrangement of the electric motor is connected to the driveshaft via an elastic connecting arrangement.
The elastic connecting arrangement between the rotor arrangement and the driveshaft allows the rotor arrangement to be centered with reference to the stator arrangement independently of an instantaneous position of movement of the driveshaft. Accordingly, the rotor arrangement can thus assume the position suitable for operating the electric machine. This self-centering is also essentially not impaired by wobbling movements present in the driveshaft to which the rotor arrangement is connected via the elastic connection.
The elastic connecting arrangement may include at least one elastically deformable connecting element. For reasons of efficient use of space, it is advantageous when the at least one elastically deformable connecting element supports the rotor arrangement in a first end region, and is constructed at a second end region for connection to the driveshaft.
In a further embodiment according to the present invention, the connecting arrangement comprises an elastically deformable connecting element constructed essentially like a disk. A radially external first end region of the disk bears the rotor arrangement and the radially internal second end region of the disk is constructed for connection to the driveshaft.
In an alternative embodiment according to the present invention, the elastic connecting arrangement may comprise a plurality of elongated connecting spring elements arranged in succession in the circumferential direction as elastically deformable connecting elements having first end regions connected to the rotor arrangement and second end regions for connection to the driveshaft.
Moreover, a drive system according to the present invention may comprise a simple design when the second end region of the at least one elastically deformable connecting element is constructed for essentially direct connection to the driveshaft.
As an alternative, the second end region of the at least one elastically deformable connecting element may be connected to the driveshaft via a supporting arrangement.
This type of configuration is particularly advantageous when the connecting arrangement comprises a plurality of elastically deformable connecting elements.
The supporting arrangement may comprise connecting sections which extend into a radial region in which the first end regions of the elastically deformable connecting elements are connected to the rotor arrangement. In this embodiment, the elastically deformable connecting elements extend essentially in the circumferential direction. However, the supporting arrangement may alternatively have connecting sections which are assigned to the elastically deformable connecting elements, wherein the connecting sections are situated radially inside a radial region in which the elastically deformable connecting elements are connected at their first end region to the rotor arrangement. In this alternative embodiment, the elastically deformable connecting elements extend radially and in the circumferential direction. This type of configuration allows the supporting arrangement to be constructed with a very simple design.
For example, the supporting arrangement may comprise a torsional vibration damper arrangement with a cover plate at which the connecting sections are provided.
In accordance with a further embodiment, the drive system according to the present invention may be constructed so that the rotor arrangement is connected or connectable to the driveshaft via a torsional vibration damper arrangement. In this embodiment, the elastically deform able connecting arrangement is provided in a region of the connection of the torsional vibration damper arrangement to the driveshaft. In this embodiment, the elasticity is situated essentially between the driveshaft and the torsional vibration damper arrangement. Accordingly, the torsional vibration damper may be decoupled with regard to the wobbling movements which may potentially occur in the region of the driveshaft.
The torsional vibration damper arrangement may comprise an elastically deformable connecting element for connecting the torsional vibration damper arrangement to the driveshaft. This elastically deformable connecting element may be constructed, for example, with a deformation region arranged in the shape of a tube. In this case, the required elasticity may be obtained in a simple way by constructing a deformation slit arrangement in the deformation region. The deformation slit arrangement comprises a plurality of deformation slits which preferably extend in the circumferential direction and follow one another axially or/and in the circumferential direction. It may be pointed out here that the tube-like deformation region may, of course, be constructed as a bellows with a corrugated wall structure providing the required elasticity.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.